= Brent C. Trela
{c}
\b[Brent C. Trela] is first author, with <Andrew L. Waterhouse>, of the 1996 study measuring isomer-specific <molar absorption coefficients> and stability of <resveratrol>. The paper reports distinct ethanol absorption maxima for <trans-Resveratrol> and <cis-Resveratrol> and examines dependence on light exposure and pH.<Resveratrol: Isomeric Molar Absorptivities and Stability by Brent C. Trela and Andrew L. Waterhouse>[Byline and Abstract; pp.1253–1257]{ref}
The contribution is quantitative: an optical signal becomes a concentration estimate only through the response factor for the actual chemical species and measurement conditions. Equal <molecular formulas> do not ensure equal optical responses.
At the reported trans-isomer maximum, $308\,\mathrm{nm}$ in ethanol, the coefficient is $30000\,\mathrm{L\,mol^{-1}\,cm^{-1}}$. An original <Beer-Lambert law> example has <absorbance> $0.300$ in a $1\,\mathrm{cm}$ path, giving
$$
c=\frac{A}{\epsilon\ell}=10\,\mathrm{\mu mol\,L^{-1}}.
$$
Using an incorrectly assumed coefficient $25000$ in the same units instead gives $12\,\mathrm{\mu mol\,L^{-1}}$, a 20 percent overestimate. The incorrect coefficient is hypothetical, not attributed to another publication.
A stable instrument reading also does not establish stable chemical composition if the preparation changes under illumination. Separating isomers by <chromatography> and controlling the sample environment can test changes hidden by a single optical channel. Trela's joint measurements therefore connect chemical identity and sample handling with the interpretation of an analytical signal.
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